Conventional memory devices made using semiconductor materials are typically fabricated using various types of material, such as silicon dioxide (SiO2), noble metals, just to name a few. Conventional fabrication techniques for semiconductor-type memories typically use deposition of thin film materials on substrates (e.g., silicon wafers), which are subsequently etched away using different types of etching procedures and etching materials. Conventional memory devices are fabricated to withstand the forward and reverse biasing of voltages in order to write data (e.g., a program operation or an erase operation) for a given estimated lifespan. Conventional techniques are problematic because typical memory devices can fail or breakdown due to the repeated application of voltages for data operations such as read and write operations. In some conventional memory technologies, memory cells that are electrically coupled with the word line and/or bit line of a memory cell that is selected for a data operation are referred to as half-selected memory cells and those memory cells can be subject to data disturbs caused by voltage potentials on their word or bit lines. Over time, data disturbs can corrupt the value of data stored in a memory cell and subsequent read operations on memory cells that have suffered to many disturbs can result in values of data that cannot be accurately determined by read circuitry, such as sense amps, for example.
In some conventional memory devices, the ability to accurately write data to a memory device is often limited by the materials, fabrication techniques, and/or structures used for the memory devices. Some conventional materials, fabrication techniques, and structures are problematic because a high resistive memory effect is not achieved by the use of those materials, fabrication techniques, and structures. A high resistive memory effect is desirable in order to determine the state of data stored in a given memory device (e.g., a programmed state or an erased state). For example, if a programmed state is a high resistance state that generates a low magnitude of read current during a read operation and an erased state is a low resistance state that generates a higher magnitude of read current during the read operation, then a high resistive memory effect results in a significant difference between the resistance of the programmed state and the erased state and a significant difference in the magnitude of read currents from erased or programmed memory devices. A ratio of 100:1 or more between the resistances of the programmed state and the erased state can result in a high signal-to-noise ratio S/N during read operations. A high S/N can be beneficial to sense amp circuitry used for generating data values (e.g., logic “0” for programmed devices and logic “1” for erased devices) based on the magnitude of the read currents. Typically, during a read operation on an array of memory devices, there are leakage currents from half-selected memory devices that flow while the read current flows through the selected memory device(s). Those leakage currents represent noise to the sense amps. A high S/N allows the sense amps to distinguish the signal that represents the read current from the signal that represents the leakage current. Consequently, the sense amps can generate a data signal that accurately represents the value of data stored in the selected memory device.
There are continuing efforts to improve technology for non-volatile memory devices.
Although the previous drawings depict various examples of the invention, the invention is not limited by the depicted examples. It is to be understood that, in the drawings, like reference numerals designate like structural elements. Also, it is understood that the depictions in the described drawings are not necessarily drawn to scale.